3‐Hydroxy‐2‐[1′‐phenyl‐3′‐(p‐chlorophenyl)‐4′‐pyrazolyl]‐4‐oxo‐4H‐1‐benzopyran as a spectrophotometric reagent for trace determination of tungsten(vi)

Abstract

3‐Hydroxy‐2‐[1′‐phenyl‐3′‐(p‐chlorophenyl)‐4′‐pyrazolyl]‐4‐oxo‐4H‐1‐benzopyran solution in acetone forms a yellow‐coloured complex with tungsten(vi) in perchloric acid medium which is extractable into chloroform after equilibration. In this study, tests were carried out on this compound and it was found to be quite stable and to obey Beer’s law. Interactions with various ions were studied and the molar absorptivity, Sandell’s sensitivity and relative standard deviation were also investigated. Job’s method, the mole ratio method and the equilibrium‐shift method were also used. The ratio of metal to ligand was measured using a method that was simpler, more accurate, sensitive, rapid and selective as compared with existing methods. This method is applicable to the analysis of various samples of varied composition.

Extractive Spectrophotometric Determination of Niobium (V) Using 3- Hydroxy-2-(4'-Methoxyphenyl)-4-Oxo-4H-l-Benzopyran as a Complexing Agent

“…The highly sensitive and reliable methods for quick determination of niobium such as atomic absorption and atomic emission are not found suitable in routine analysis because of their high cost and the requirement of a separate lamp source for each element to be determined. The literature survey on the methods of extraction and spectrophotometric determination of niobium reported in the past, employing benzopyrans as complexants [3][4][5]11,14], reveal that there is still a lot more to be done regarding rapidity, selectivity and sensitivity to find their usefulness concerning the analytical chemistry of niobium. With this end in view, 3-hydroxy-2-(4'-methoxyphenyl)-4-oxo-4H-1-benzopyran(HMPB) has been used for the first time in a spectrophotometric determination system involving niobium in microgram amounts.…”

“…Various existing methods [1][2][3][4][5][6][7][8][9][10][11][12][13][14] of spectrophotometric determination of niobium(V) suffer from interferences from a large number of foreign ions like Ti, V, Mo, W, Pt, Re, U and Ta. The methods are usually time consuming [1,[3][4][5], though sensitivity is slightly improved in a few cases.…”